Mayfly Burrows in Firmground of Recent Rivers from the Czech Republic and Poland, with Some Comments on Ephemeropteran Burrows in General

Abstract

ABSTRACTU-shaped, pouch-like burrows with parallel limbs, covered with short scratches arranged in sets, occur in the thalweg of the Ohře river in NW Czech Republic. Similar, but smaller burrows with rare scratches, not arranged in sets, occur in the thalweg of the Drwęca river in N Poland. Probably, they are produced by larvae and/or nymphs of Palingenia and Polymitarcis (Ephoron), respectively. In both localities, they burrowed in firmground surfaces at shallow depths. The burrowed surfaces were emerged during low water levels. A review of recent mayfly burrows shows that they are 1) U-shaped pouches with parallel limbs and septum, which may be covered with short scratches and are oriented perpendicular to the bottom, irrespective of its inclination, or 2) wide U-shape burrows with divergent limbs, which may be branched. In the fossil record, the ichnogenera Fuersichnus, Asthenopodichnium, and Rhizocorallium are partly ascribed to mayfly burrows, but their comparison to the recent burrows shows that such interpretations are somewhat problematic. The mayfly burrows are potentially good indicators of aquatic, non-marine, well oxygenated, clean water environments.